Mistletoe Tyrannulet is a common and familiar small flycatcher of Central America and neighboring parts of Colombia. It feeds heavily on mistletoes (with fruits and insects rounding out their diet), and is found in habitats where mistletoes are common, including forests, forest edges, orchards, and pastures interspersed with trees. Mistletoe Tyrannulet primarily occurs in the lowlands and foothills. It is readily identified by its distinctive wing markings: the olive-green wing feathers are outlined in yellow (thicker on the leading edge of each feather), but do not form wing bars. Mistletoe Tyrannulet easily can be easily overlooked, but can be located by its frequently uttered, plaintive peeer or peeeu call. Mistletoe Tyrannulet formerly was but one subspecies in a polytypic Paltry Tyrannulet Zimmerius vilissimus, which now is recognized as four separate species: Guatemalan Tyrannulet (Zimmerius vilissimus), Mistletoe Tyrannulet, Spectacled Tyrannulet (Zimmerius improbus), and Venezuelan Tyrannulet (Zimmerius petersi). The biology of all four species probably is similar, but most of them are very poorly known; Mistletoe Tyrannulet is the only member of the group that has been studied in life.